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Cynthia Kenyon Cynthia Kenyon as seen on Never Say Die: Wisdom of the Worms

Click on Cynthia's photo to read a brief bio.



q I found your work really fascinating! What specifically is the genetic change that allows your mutant nematodes to live twice as long as normal? (Question from Robert)

A There are now many different genetic changes that extend lifespan. Some of the changes in the receptor affect the part of the protein that binds the hormone. Others affect the part of the protein that is inside the cell. These changes were identified by the lab of Gary Ruvkun at Harvard. It is also possible to extend lifespan by changing other genes that are needed for the body of the worm to respond correctly to the hormone.


q Do have any plans to expand your age-extending experiments with other types of animals, other than the nematodes you're currently working with? (Question from Mark S.)

A Yes, we are beginning to study mice as well as nematodes.


q In your story, we learned that genetic changes and blocking hormone receptors on cells can increase lifespan. In another story, at the Geron Corp., we saw that preserving telemeres can extend cell life. If there any connection here? Or is your research and the work at Geron taking two different approaches? (Question from Kathryn)

A It is unlikely that changes in telomeres are influencing the lifespan of the worm. That is because telomeres only shorten when cells divide. Most of the cells of the worm stop dividing when the worm becomes an adult.


q Thanks for appearing on "Never Say Die." I enjoyed learning about your work, and I'd like some of that stuff right away, please. Alan Alda asked what possible reason an organism would have to cause its own demise, and you said, essentially, nobody knows. I always thought that it would be beneficial for the old generation to get out of the way for the new one. Otherwise, the old guys would be around competing with the new guys, who hopefully have the better genes. Is this a completely wacko idea? (Question from Bob)

A I like your idea. Here is my favorite idea: In the presence of food and low population density, worms reproduce rapidly, producing 300 progeny in the first three days of adulthood. That's an amazing rate of compounding. (Imagine your 401k compounding at a rate of 300% every three days. Soon you would own everything (very soon).) For the worm, this is a strategy that converts whatever the worms are eating into more worms very rapidly. Now, I didn't say this on the TV show, but we know that the long-lived mutants are resistant to damage caused by oxygen (free radicals, which produce oxidative damage) and other environmental stresses. We also know that at least some genes, like a gene encoding the protein superoxide dismutatase (which prevents free radical damage) are expressed at very high levels in these long-lived worms. It seems to me that it would be energetically more expensive to produce such a "superworm". Therefore, a population that did this (used some of its food to make the worms more resilient than then need to be just to produce their 300 progeny) might lose out to one a population that converted every drop of food into more worms.


q What chemicals do you bathe the nemotodes in to cause the genetic changes that prolonged their life span? After you bathed the nematodes in the chemical bath, were they the worms that lived longer, or was it the next generation that lived longer? (Question from Bierit)

A We treat the worms with EMS (ethyl methane sulfonate). It causes mutations (changes in the bases of their DNA). We examine the descendants of the worms for changes in lifespan. Worms are self-fertilizing hermaphrodites. That means that the mutants appear among the grandchildren of the worms we treat with the chemical.


q Why did you decide to do your research with nematodes? Wouldn't it be easier to work with a larger creature? (Question asked by several viewers)

A There are three reasons we work with nematodes:
  1. They have a very short lifespan--just a little over two weeks.
  2. It is possible to identify genes that regulate aging by making random mutations (changes) in the DNA. That way we can take an unbiased approach to the study of aging.
  3. Even though they don't look much like us, we know that they use very similar mechanisms as we do to control their growth and development.

q Can you tell me how I can continue to get up to date information on your work and the many advances currently being discovered/made on this very fascinating subject. (Question asked by several viewers)

A Scientific American is going to have a whole issue devoted to aging pretty soon. I suggest keeping an eye out for that publication (sometime in the next few months).


q When, and how, do you think scientists can apply what you know about the worms to humans? (Question from JGiggles)

A That's hard to say. If the aging process is controlled in a similar way in worms and humans, then we can use what we learn about worms to speed our study of higher organisms. I would say we would know a lot in the next ten years. On the other hand, if it turns out that humans age in a fundamentally different way from worms, it may take us a lot longer!


q After inhibiting hormones or other substances were added to the cell receptors in the worm's body, were there any other visible side effects besides living longer? (Question from Armando, biology student at San Francisco State University)

A The gene we changed to make the animals live long has several functions in the animal. But it is possible to change it in such a way that the animals seem to be completely healthy and fully fertile, but they still live twice as long as normal. They are more resistant than normal worms to high temperature and to oxidative damage. This may be related to their long lifespans, but we don't know for sure. If I were a worm, I would rather be the long-lived mutant than the normal worm, that's for sure.


q I was wondering how you figured out the way that the hormone messengers are received? Can you see them with a microscope? Thank you! (Question from REBREK6)

A Studies of hormone systems in humans have told us the DNA sequences of the genes that make the hormone receptors. When the gene we showed regulates lifespan (called daf-2) was isolated (by the laboratory of Gary Ruvkun at Harvard), it was possible to tell that it was a hormone receptor by comparing its DNA sequence to known DNA sequences in humans.


q Do you know of any organisms that try to beat death, or is it in all of nature that organisms have a preset time of death? (Question from Dan)

A I think bacteria may be immortal, and of course the germ line (sperm and oocytes) is immortal. Some animals live a really long time--like certain fish and turtles, which can live 150-200 years. Redwood trees, of course, can live for thousands of years.




 

Scientific American Frontiers
Fall 1990 to Spring 2000
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